1. Technical Field
One or more embodiments of the present invention relate to a relay station and a relay method for relaying communication between a user apparatus and a base station
2. Background Art
In a cellular mobile communication system, in order to enlarge coverage of a cell and/or in order to realize load distribution in a base station (eNB), there is a case where a relay station (relay node: RN) is provided between the base station (eNB) and a user apparatus (UE). The base station (eNB) in this case functions as a parent station, and may be referred to as a donor base station (donor eNodeB: DeNB). However, as long as there is no fear of confusion, a donor base station as well as a base station which is not a donor base station may be referred to as eNB. Although the user apparatus (UE) is a mobile station typically, it may be a fixed station. A radio interface between the base station (eNB) and the relay station (RN) is referred to as “Un”. A radio interface between the relay station (RN) and the user apparatus (UE) is referred to as “Uu”.
FIG. 1 shows protocol stacks on a user plane of various nodes in a communication system. FIG. 1 shows protocol stacks of each of a user apparatus (UE), a relay station (RN), a base station (DeNB) and an opposing node. The opposing node is a node which is a communication partner of the user apparatus (UE). The user apparatus (UE) includes, in order from the higher layer, an application layer, a TCP/IP layer, an IP layer, a PDCP layer, an RLC layer, a MAC layer and a PHY layer. The relay station (RN) includes, in order from the upper layer, a PDCP layer, an RLC layer, a MAC layer, and a PHY layer, for communication with the user apparatus (UE). Also, for communication with the donor base station (DeNB), the relay station (RN) includes, in order from the upper layer, a GTP layer, a UDP layer, an IP layer, a PDCP layer, an RLC layer, a MAC layer, and a PHY layer. Also, for communication with the relay station (RN), the donor station (DeNB) includes, in order from the upper layer, a GTP layer, a UDP layer, an IP layer, a PDCP layer, an RLC layer, a MAC layer, and a PHY layer. Also, for communication with the opposed node, the donor base station (DeNB) includes, in order from the upper layer, a GTP layer, a UDP layer, an IP layer, an L2 layer, and an L1 layer. The opposed node includes, in order from the upper layer, an application layer, a TCP/IP layer, an IP layer, a GTP layer, a UDP layer, an IP layer, an L2 layer and an L1 layer. Such a communication system is described in “3GPP TR36.806 v9.0.0 (2010 March) (FIG. 4.2.2-4)”.